Students will
- Read a button with a defined resting state
- Control a current-limited LED
- Trace input, decision, and output in a sketch
Arduino Uno R3
Button to signal
Build a stable digital input, control a protected LED, and explain how a physical action becomes program behavior.
MS-PRO-RD-17ProgrammingMS-PRO-TR-19Programming
Evidence of success
- LED responds consistently to at least five presses
- Serial output agrees with the physical button state
- Student identifies the input, decision, and output lines
Hardware
- Arduino Uno R3
- Momentary pushbutton
- LED
- 220 Ω resistor
- Breadboard and jumper wires
Prerequisites
- Identify 5V, GND, and digital pins
- Upload a sketch
Before class
- Verify the button's internally connected leg pairs
- Confirm LED polarity and resistor value
- Open Serial Monitor at 9600 baud
Reviewed connection map
Input, decision, and protected output
- Connect the button between D8 and GND; verify which legs are internally paired.
- Connect D9 through one 220 Ω resistor to the LED anode, then connect the LED cathode to GND.
- Test the button input and protected LED output separately before running the combined sketch.
Build and test
- 01Test the LED output independently
- 02Wire the button from D8 to GND and configure INPUT_PULLUP
- 03Observe released HIGH and pressed LOW
- 04Combine the input with the LED output
- 05Repeat the test and record evidence
Read before uploading
Annotated Arduino sketch
const int BUTTON_PIN = 8;
const int LED_PIN = 9;
void setup() {
pinMode(BUTTON_PIN, INPUT_PULLUP);
pinMode(LED_PIN, OUTPUT);
Serial.begin(9600);
}
void loop() {
const int buttonState = digitalRead(BUTTON_PIN);
const bool isPressed = buttonState == LOW;
digitalWrite(LED_PIN, isPressed ? HIGH : LOW);
Serial.println(isPressed ? "pressed" : "released");
delay(50);
}
Optional engineering record
Record evidence from this lesson
Choose the prompts that help students explain predictions, evidence, debugging, and transfer. Saving creates a new entry in this browser’s Rudi notebook.
Record your thinking — optional4 prompts
Use these prompts if they help students capture evidence, decisions, or questions. You do not need to complete every prompt or create an entry at every step.
Nothing is saved until you choose this button.
Troubleshooting
Input changes without a press
Confirm INPUT_PULLUP and the button-to-GND connection.
LED never lights
Test polarity, resistor placement, GND, and the D9 wire independently.
2026 middle school standards
Potential CSTA connections
These are evidence-based crosswalk candidates for curriculum review—not a claim of official alignment.
Analyze the roles of iteration, selection, variables, and procedures in a segment of code.
Students trace variables, selection, or iteration in the supplied sketch and connect code to physical behavior.
Lesson evidence: Input–decision–output code traceUse systematic strategies to test, refine, and document changes to a computing technology to meet the intended purpose.
Students isolate variables, compare observed behavior with the intended purpose, and document a revision.
Lesson evidence: Five-trial response recordSupporting concepts
floating-inputs · ohms-law · power-and-signals
Sources and review
Arduino Uno R3 documentationArduino Projects Book · CC BY-NC-SA 3.0Starting point, not verified curriculum. Review the actual hardware, circuit, code, power requirements, and classroom conditions.
After teaching this lesson